This invention relates to optical radiation sensor apparatus.
The invention is more especially, but not exclusively, concerned with optical pyrometer apparatus.
Optical pyrometer apparatus are used for measuring high temperatures in for example, gas-turbine engine and furnaces. The pyrometer apparatus includes a radiation receiving head, a radiation detector which produces an electrical output, a preamplifer for amplifying the detector output, and utilizing apparatus for scaling, comparison and calculation on the preamplified output of the detector to provide an output suitable for display of temperature, data storage, performance of a control function and so on.
The radiation detector may be contained in the receiving head so that an electrical output is produced, but there are advantages to mounting the detector remotely and interconnecting the detector and receiving head by a flexible radiation guide, such as a fibre-optic cable. In this way, the detector can be mounted at a cooler location. Such fibre-optic pyrometers, therefore comprise three separate units: the pyrometer head; the detector and preamplifier or other signal conditioning unit; and the utilising apparatus. The pyrometer head is connected to the detector by a fibre-optic cable: the detector is connected to the utilization apparatus by an electrical cable. Other similar optical radiation sensor apparatus are also divided into three units interconnected by cables.
Such apparatus has several disadvantages. The electrical cable and connectors between the detector and utilization apparatus adds to the overall weight of the pyrometer, especially where the cable is screened which is usually necessary in aircraft applications. The cable and connectors can also be susceptible to electromagnetic interference. The detector must also be clamped, screwed or otherwise secured in place, making installation more difficult.